Abstract. In the same fashion that a memory cache arranges for machine instructions and data that are frequently accessed to operate from high speed memory, the functionality cache installs hardware implementations of frequently executed code sequences in reconfigurable hardware. Code sequences become candidates for instantiation as hardware if the benefits outweigh the costs over some accounting period. Algorithms are provided for converting sequences of stack manipulations characteristic of executable Java programs into systolic processing circuitry and mapping that machinery into networks of FPGAs (Field Programmable Gate Arrays).